This invention relates to a process for producing non-woven fabrics of carbon fibers. More particularly, it relates to a process for producing non-woven fabrics in which adhering points supporting the non-woven fabrics structure are the same carbon materials with the component fibers and which is superior in strength, dimensional stability, heat-resisting property, chemical resistance, electric conductivity, etc.
Since the non-woven fabrics produced according to the process of the present invention are constructed with carbon materials, i.e., not only the fibers but also even adhering points are constituted with carbon materials, the fabrics have advantages that they can fully exhibit superior physical and chemical characteristic properties of carbon materials.
The production of non-woven fabrics which utilize self-adhesion of fibers is widely put into practice in case of synthetic composite fibers in which a higher melting point polymer of core and a lower melting point polymer of sheath are combined.
In case of carbonized fibers, since there is substantially no softening point, adoption of the same process with synthetic fibers is impossible. However, it is possible to cause self-adhesion in the stage of precursor fibers. For example, Japanese laid open patent application No. Sho 50-101405 describes to produce non-woven fabrics by self-adhesion of lightly or not infusiblized pitch fibers. However, in this application, it is inferred that the behavior of the fibers is considerably different from pure pitch fibers, because a large amount of silicon compound and alumina are mixed therein. It is inferred that silicon compounds and alumina suppresses the deformation of the pitch which is at the higher temperature than its softening point, performs by such a behavior as the core component of composite fibers of synthetic fibers and prevent pitch fibers from turning into droplets. It is not suggested that non-woven fabrics are formed by self-adhesion of pure pitch fiber.
In the Japanese laid open patent application No. Sho 52-47014, there is disclosed a process in which lightly or not infusiblized pitch fibers are formed beforehand into an arbitrary shape and thereafter made into a porous shaped body by self-adhesion. This process is superior as a production process of a porous shaped body, but if it is evaluated as a production process of non-woven fabrics, there is a problem that since change of shape of the pitch fibers is so great that resulting non-woven fabrics are of high density and hard products like a fiber-board which is difficult to handle as a cloth.
It is an object of the present invention to provide a process which can overcome the problem of the non-woven fabrics of pitch-based carbon fibers produced by self-adhesion according to conventional process of art and having so great a density that handling as a cloth is difficult, and which enables to produce non-woven fabrics constructed with carbon materials both in fibers and in binder at an inexpensive cost.